A worldwide manufacturer of many types of plastic has manufacturing facilities around the world, including one in the southeast that makes PVC stretch film. Imagine the film used to wrap meat at your local neighborhood grocery store, or that you might use to keep leftovers fresh for later in the week. Although the plant is designed for precision and automation, sometimes mechanical components derail those plans and require operator interaction to correct the components shortcomings.  The clutch-brake on a turret winding system was not precise, which not only required operator interaction but also caused downtime.  Replacing the dry clutch brakes with Force Control Oil Shear clutch brakes eliminated downtime, increased accuracy and repeatability, and slashed operator involvement – all while increasing throughout.

This facility has eight blown film extrusion lines.  Clear plastic is extruded and blown into a bubble, then collapsed into a thin plastic sheet.  This sheet then goes to a winding machine where it is wound into rolls on dual shaft turrets, each fitted with a clutch brake.  One shaft is on the winding drum winding the plastic into rolls, while the other awaits its turn.  When the winding roll trips a footage marker, the air-actuated clutch-brake engages and indexes the turret, flipping it away from the winding line and bringing the second shaft into the winding drum. At least that is the plan.  

The previous air operated clutch brakes that were positioning the turrets were lacking precision and repeatability.  So, an operator had to manually reposition the turret so that it could integrate into the next step of the downstream process.

“We were having so many issues when we would flip and index, we could never hit the same spot,” recalls the plant manager. Left unchecked, the inconsistency would wreak havoc with the downstream automation.  

“Since the turret with the completed rolls was not level, it wouldn’t flow properly on the automated downstream equipment. Things would jam up.”

And that would require even more operator involvement and possible downtime. So, they installed a leveling device to try to bring the turrets back into a workable position. Once the turret indexed a cylinder on the leveling device would actuate, and rock the turret into a more acceptable position. “It just wasn’t successful,” recalls the plant manager.  “It didn’t always work, and the levelers required a lot of maintenance.”  

Company officials estimate that of the 16 levelers across the eight blown film lines, they were repairing one a week.  Doing so equites to at least a couple hours of downtime, and lost production time.  

Even without the downtime, the unlevel turrets required operator involvement to alleviate the jam or downstream integration issues with the automated downstream equipment. “Our operator would either manipulate the shaft or some other equipment to get it seated properly to allow it to continue its journey downstream. It was unnecessary operator involvement because this is supposed to be automated.”

Operator involvement typically involved pushing a button that would release the brake and allow them to manually manipulate it.  That was done with a metal rod like a crowbar.  They’d pry the turret to level it back out and then re-engage the brake, allowing the turret and its contents to proceed downstream. 

Frustrated with the amount of both downtime and operator involvement required to operate with the old clutch brakes, the plant manager started Googling terms like indexing, precision, level, and others she equated to their process.  An article from Force Control published in 1998 which described the then-new idea of closed-loop positioning control (CLPC) paired with clutch brakes popped up. Clicking the link to their website, and looking around, lead the manager to contact Regional Manager Jim McHugh, who thought it would work.  “Somehow, I convinced upper management to give it a shot and I’m glad we did because it works great. “ 

Although both the old clutch brakes and the new Posidyne models are both air actuated, that’s where the similarities stop. Posidyne clutch brakes feature oil shear technology for rapid and precise stopping, starting, speed change and positioning, all without adjustment or maintenance. Ideal for applications with frequent start/stop cycles, such as indexing turrets, these unique motion control devices allow higher cycle rates (up to 300 cycles per minute), to increase production rates with lower downtime. Faster production rates and significantly longer service life than traditional (dry) clutch/brakes (often 5 to 10 times longer) yields increased uptime, productivity and ROI. Posidyne clutch/brakes are field proven in diverse applications such as packaging lines, food and chemical processing facilities, lumber mills, shingle plants, fiberglass insulation production, metalworking, and many more.

Designed with low inertia cycling components makes the Posidyne clutch brake more efficient, requiring less motor horsepower to accelerate the load, and less torque to stop the load. Their totally enclosed design is impervious to dust, chips, chemicals, coolants, caustic wash down, weather, and more, making them ideal for hostile environments.  

Posidyne clutch/brakes feature a multiple disc design that produces high torque from a small package. Re-circulating the fluid dissipates the heat of engagement, which is a common cause of downtime with other clutch/brake assemblies.

A simple actuation system allows torque in the clutch and brake to be precisely controlled independently.  Adjustment for rapid or soft starts and stops is easily accomplished. In this instance the clutch is operating ad 30 psi while the brake is set at 20 psi: ideal for smooth, accurate actuation of both the clutch and the brake. The old clutch brakes had no means of controlling the incoming air pressure, so the stops were jarring, shortening their life and those of nearby components like gearboxes and bearings. 

An encoder on the clutch brake as part of the CLPC allows precise stopping every time without the need for the leveling device (and thus the inherent downtime for its maintenance and repair). 

forcecontrol.com